On what date was Auschwitz-Birkenau liberated by Soviet troops during World War II?

Auschwitz-Birkenau was liberated by Soviet troops on 27 January 1945.

Soldiers of the Soviet Union’s 60th Army, part of the First Ukrainian Front, entered the Auschwitz camp complex in German-occupied Poland. They found about 7,000 prisoners who had been left behind because the SS had evacuated many others westward on death marches. The prisoners were severely ill and malnourished, and the camp contained extensive evidence of Nazi crimes.

Auschwitz had functioned as a concentration and extermination camp complex from 1940 until its liberation. More than one million people, mostly Jews, were murdered there. The liberation date is commemorated internationally as International Holocaust Remembrance Day, established by the United Nations in 2005.